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  <script>
    // 使用for循环 - 求出数组元素的和 [5, 8, 9, 2, 1, 5]

    let arr = [5, 8, 9, 2, 1, 5]
    let sum = 0
    for(let i = 0;i<arr.length;i++){
      sum += arr[i]
    }
    console.log(sum);

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